Can filling devices typically utilize an annular sleeve, commonly referred to as a "tulip" which engages the top of an empty can. The mechanism includes passageways for allowing gravity flow into the can of the beverage liquid and a central tube for introduction of carbon dioxide gas into the can. The carbon dioxide gas is introduced for the purpose of flushing out any air from the interior of the can and to charge the can. Opening of the central tube also equalizes pressure in the system, allowing liquid to run into the can. The central tube has a stem at the top thereof which is engaged by a bifurcated lever and raised and lowered to cause opening and closing of a valve at the top of the tube, thereby starting and stopping the flow of carbon dioxide gas into the can.
The forked or bifurcated lever used to control the opening and closing of the stem valve is raised and lowered by rotation of a shaft with which it is integral. The opposite end of the shaft from the bifurcated lever has a two-pronged handle secured thereto commonly referred to as a "butterfly". Opening of the needle valve is accomplished by pushing downwardly on the uppermost arm of the butterfly to rotate the shaft in one direction, whereas closing thereof is caused by passage of the lower arm of the butterfly along a cam surface, which causes rotation of the shaft in the opposite direction. Generally the cam surface is a stationary track and the can filling apparatus is traveling in a circular path wherein the butterfly is acted on by the cam surface at an appropriate position required for closing of the needle valve at the appropriate time in the can filling cycle.
In accordance with current practice the shaft carrying the bifurcated lever is caused to rotate by extension against the upper butterfly arm of an extendible and retractable shaft which is actuated by an pneumatic cylinder. The extendible/retractable shaft has a blunt end with rounded edges which is of a small diameter and spaced so as to strike the butterfly arm at a point offset from the central axis of the rotatable shaft.
Due this design, the upper arm of the butterfly routinely wears out or becomes grooved or gouged by repeated action there against of the extendible arm. Also, the rotatable shaft, itself, becomes loosened in its bearings due to the torque applied by the off-axis impact of the end of the extendible rod. The rotatable shaft is desirably frictionally held so as to avoid free rotation thereof. When worn, the shaft will rotate too easily so that the needle valve may open too rapidly and thereby be allowed to impact against other parts of the mechanism usually, the top of the beverage-containing reservoir, eventually causing the needle valve to fail. Failure of this mechanism causes a substantial loss in terms of down time, wasted beverage and various problems caused by the need to disassemble the can filling apparatus.
In view of the foregoing problems, a need has existed for improved mechanisms for controlling the valves in can filling equipment.